netdev - [PATCH iproute2] lib/libnetlink: fix response seq check

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Message-Id: <20180928171339.4332-1-vlad@dumitrescu.ro>
Date:   Fri, 28 Sep 2018 13:13:39 -0400
From:   vlad@...itrescu.ro
To:     stephen@...workplumber.org
Cc:     chrism@...lanox.com, netdev@...r.kernel.org, maheshb@...gle.com,
        Vlad Dumitrescu <vladum@...gle.com>
Subject: [PATCH iproute2] lib/libnetlink: fix response seq check

From: Vlad Dumitrescu <vladum@...gle.com>

Taking a one-iovec example, with rtnl->seq at 42. iovlen == 1, seq
becomes 43 on line 604, and a message is sent with nlmsg_seq == 43. If
a response with nlmsg_seq of 42 is received, the condition being fixed
in this patch would incorrectly accept it.

Fixes: 72a2ff3916e5 ("lib/libnetlink: Add a new function rtnl_talk_iov")
Signed-off-by: Vlad Dumitrescu <vladum@...gle.com>
---
 lib/libnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index f18dceac..4d2416bf 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -647,7 +647,7 @@ static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iov,
 
 			if (nladdr.nl_pid != 0 ||
 			    h->nlmsg_pid != rtnl->local.nl_pid ||
-			    h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
+			    h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen + 1) {
 				/* Don't forget to skip that message. */
 				status -= NLMSG_ALIGN(len);
 				h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
-- 
2.19.0.605.g01d371f741-goog